Aqueous explosive gel composition and process



United States Patent 3,160,538 Aounousnxrrosivn nun eorurosrrrotv AND rnoeess Joel A. Zaslowslry and James S. Logan, Woodhridge,

Comm, assignors, by mesne assignments, to Commercial Solvents Corporation, a corporation of Maryland No Drawing. Filed July 1, 11963, fier. No. 2%,074 18 Claims. (Cl. 149- 23) This invention relates to blasting explosives. More particularly, this invention relates to substantially water resistant, explosive gels containing ammonium nitrate.

Blasting explosives in aqueous slurry or gel form have been used extensively heretofore. When such blasing explosives contain nitroglycerin, there is an ever present danger of accidental detonaton as Well as the headacheproducing effect of the nitroglycerin vapors. There is also a possibility of accidental detonation of aqueous slurry type and gel type blasting explosives which contain trinitrotoluene and for other high explosives. Y More recently blasting explosives have been made available in the form of aqueous slurries of ammonium nipower of the blasting explosive is reducedsigniiicantly.

There is a great need at the present time in the blasting industry for a pourable blasting explosive whichis free from unprogrammed explosion hazards, noxious fume hazards, and which is substantially resistant to penetration by water or otherfiuids normally encountered in blasting environments.

It is a primary object of this'invention to provide a novel blasting explosive which overcomes the disadvantages inherent in blasting explosives available in the prior art, and which supplies the needs of the blasting industry.

A further object of theinvention is to provide a blas"- ing explosive gel which is substantially devoid of oversensitive components.

Still another object of the invention is to provide a novel explosive gel which is substantially devoid of noxious fumes. 7

It is another object of the invention to provide a novel process for preparing water resistant explosive gels.

Another object of the invention is to provide a novel process for preparing blasting explosives.

Theseand other objects of the invention will be apparent from the following detailed description thereof. It has now been discovered that a pourable, substan- 1 tially-water-resistant explosive gel is formed by. admixing ammonium nitrate, hydrochloric acid, metal particles, and Water with a gel forming proportion of a mixture of guar gum and glutaraldehyde. The novel blasting explosive gel ofthis inventioncan be stored for extended periods without the dangerof unprogrammed explosion and Without the emission of noxious fumes. In addition the novel blasting explosive gel of this invention may be poured into water, for example, into a bore hole containing water, without the danger of significantdissolution of the gel by the water contained in the bore hole.

Ammonium nitrate in any convenient form, such as commercially available crystals, prills, and the like, may

be employed. The particle size of the ammonium nitrate is not critical, and any size that is readily dissolved in water is preferably used.

Hydrogen chloride or hydrochloric acid is employed to permit cross linking of the novel explosive gel of this invention. Hydrogen chloride may be employed as a gas which is bubbled into an aqueous solution of ammonium nitrate prior to gelation, or aqueous solutions of hydrochloric acid may be employed. Sufiicient hydrochloric acid is employed in the preparation of the novel explosive gel composition to adjust the pH of the gel to between about 1.5 and about 4, and preferably between about 2.5 and about 3.5. Other acids such as oxalic, sulfuric, and phosphoric may be employed to replace part or all of the hydrochloric acid. 1

A powdered metal such as powdered aluminum, powdered magnesium, and mixtures thereof, is added with agitation to the aqueous acidic solution of ammonium nitrate, or to the gel formed therefrom. The powdered metal may be in either the atomized form or the flake form, or any other convenient form so long as the particle size is small enough to permit the particles to pass through an 80 mesh standard screen, and preferably through a 100 mesh standard screen.

The viscosity of the aqueous acidic solution of ammonium nitrate containing powdered metal is increased by the incorporation therein of a suitable thickening agent such as guar gum, and a small proportion of a crosslinking agent such as glutaraldehyde. The gel forming ingredients, guar gum and glutaraldehyde, serve to maintain the resulting mixture in a water resistant gel form. These agents do not prevent contact between the ammonium nitrate and the Water originally in the explosive composition, but they do prevent additional water from entering into the composition and leaching out the explosive ingredients. This characteristic permits the novel composition of this invention to be charged into wet locations such as bore holescontaining water or other targets submerged under water without mixing with the water surrounding the charge. In such :an operation, the composition falls as a substantially-immiscible liquid through the water to the bottom of the bore hole. In the absence of the cross-linking agents, the explosive composition dissolves in water, thus resulting in severe dilution of the ammonium nitrate and in dissipation of. the explosive strength of the composition.

Listed below are the operating proportions and the pre ferred proportions, in. percent by weight, of the components' employed in making the novel blasting explosive of this invention.

Operating Preferred Proportion Proportion Components Ranges, Ranges,

Percent by Percent by Weight Weight Ammonium Nitrate 5-90 40-70 1101 0. 01-2. 0 0.5-1.0 0. 03-5. 0 1. 0-3. 0 0. 03-2. 0 0. 5-1. 0

drous form, or it may be employed to form a solution and/ or slurry with some or all or" the components of the explosive composition prior to mixing. The novel gel forming effect may be obtained when the metal is omitted but'detonation of the gel becomes more difficult.

iii

In another embodiment of the invention, the gelling agents are added stepwise to permit hydration of the guar gum. For example, about 70 percent of the guar gum is added to the acidic aqueous solution of ammonium nitrate and permitted to hydrate for about two minutes. Then about 20 percent of the glutaraldehyde is added to the resulting mixture and stirred for about three minutes. The remainder of the glutaraldehyde is then added to the resulting syrupy solution. A mixture of aluminum powder, magnesium, and the remainder of the guar gum is then added with stirring for an additional three minutes. Other variations in the order of mixing of the ingredients may be employed without departing from the spirit of the invention.

The following examples are presented to further illustrate the invention without any intention of being limited thereby. All parts and percentages are by weight unless otherwise indicated.

Examples l-4 Three ammonium nitrate solutions were prepared, designated as solutions A, B, and C, respectively, each containing 75 grams of ammonium nitrate dissolved in 22 grams of water. Guar gum, in the proportions indicated below, was added slowly to each ammonium nitrate solution with stirring until a homogeneous syrup was obtained. Three milliliters of a 25 percent aqueous solution of glutaraldehyde was stirred into the syrup followed by the addition of concentrated hydrochloric acid in the proportions indicated below. in the treatment of solution C, 0.5 gram of guar gum was first admixed with the ammonium nitrate solution, then the glutaraldehyde was added, and then 2.0 grams of guar gum were added, followed by the addition of hydrochloric acid. After standing for about 3 hours a resilient gel was obtained in each instance. A fourth ammonium nitrate solution, designated as solution D, was prepared by dissolving 82 grams of ammonium nitrate in 18 grams of water. To this solution was added 2.5 grams of guar gum slowly with stirring followed by the addition of 3 milliliters of a 25 percent aqueous solution of glutaraldehyde and the proportion of concentrated hydrochloric acid listed below. After standing for about 3 hours, a resilient gel formed.

A weighed sample of each gel formed from solutions A, B, C, and D, respectively, was placed in four separate beakers, and 100 milliliters of water were then poured over each gel. After 6 hours, the supernatant liquid was poured off and its weight, volume, and density were determined. From these data the amount of ammonium nitrate which had dissolved in the water was calculated. Listed below are the proportions of ingredients employed in preparing the gels, and the percent of ammonium nitrate leached from the gel by Water.

These examples demonstrate that only a small proportion of ammonium nitrate was leached from the gels.

Example A 75 percent aqueous ammonium nitrate solution was admixed with 1.5 grams of guar gum until a homogeneous syrup was formed. One milliliter of an aqueous 25 percent solution of glutaraldehyde was then added to the syrup followed by the addition of l milliliter of concentrated hydrochloric acid and 20 grams of powdered aluminum. Stirring of the mixture was continued until the powdered aluminum was substantially uniformly dispersed therein. A resilient gel formed after the resulting mixture was allowed to stand for about 2 hours.

A portion of the gel was weighed and then allowed to stand at room temperature for about 16 hours and then reweighed. During this period the gel had a weight loss of about 2.8 percent.

Example 6 The procedure of Example 5 was repeated with the exception that 2.0 grams of guar gum and 0.5 milliliter of concentrated hydrochloric acid were added to the ammonium nitrate solution along with glutaraldehyde and powdered aluminum in the proportions of Example 5. The weight loss of the resulting gel was 2.2 percent.

Examples 7-9 An aqueous ammonium nitrate solution was prepared by dissolving 75 grams of ammonium nitrate in 25 grams of water and a gel was prepared in accordance with the technique of Example 5 by adding to the solution 2.5 grams of guar gum, 3.0 milliliters of a 25 percent aqueous solution of glutaraldehyde, 15 grams of powdered aluminum, and 0.1 milliliter of concentrated hydrochloric acid. The resulting gel was designated as Gel A.

A gel similar to Gel A was prepared with the exception that 0.1 gram of powdered magnesium was added with the powdered aluminum. The resulting gel was designated as Gel B.

Another gel was prepared in a similar manner with the exception that 0.2 gnam of powdered magnesium was added with the powdered aluminum. This gel was designated as Gel C.

The density of sample Gels A, B, and C were found to be as follows:

Density, Example per cc.

Examples 10-13 An explosive gel was prepared by the technique similar to that of Example 5 by admixing with 75 percent aqueous solution of ammonium nitrate and about 2.5 grams guar gum, 3.0 milliliters of a 25 percent aqueous glutaraldehyde solution, 15 grams of powdered aluminum and 0.1 milliliter of concentrated hydrochloric acid. The resulting gel, which was designated as Gel D, was placed in a paper cup in a hole in the ground so that the top of the explosive gel charge was even with ground level. An Engineers Special electric detonator was placed in the charge and fired and the volume of the resulting crater was measured. Gel E was prepared in the manner similar to Gel D with the exception that an additional 0.15 milliliter of concentrated hydrochloric acid was employed.

In a similar manner Gels F and G were prepared with the exception that an additional 0.4 and an additional 0.9 milliliter of concentrated hydrochloric acid, respectively, were employed. Each gel was fired in the same manner,

using an Engineers Special electric detonator. The crater volume obtained with each explosion was as follows:

Crater Volume, cubic inches Example G 2, ass 1, 650 s, 270

Examples -13 demonstrated that generally the explosive power of the gel is increasedwith an increase in the content of hydrochloric acid.

. Example 14 An explosive gel of this invention was prepared by a technique similar to that of Example 5 employing the following ingredients in the following proportions.

The resulting gel was then detonated, employing a tetryl booster (10 parts). The resulting crater corresponded in size to that formed by detonating an equivalent weight of 60 percent dynamitegel.

For purposes of comparison, an aqueous solution of ammonium nitrate (50 parts Water and 50 parts ammonium nitrate) were admixed with 1.75 parts of guar gum and 15 parts of flaked aluminum. No gel formed and after 48 hours the aluminum flakes settled to the bottom of the slurry.

Various modifications of the invention, some of which have been referred to above, may be employed without departing from the spirit and scope of this invention.

What is desired to be secured by Letters Patent is:

1. An acidic explosive gel composition comprised of ammonium nitrate, water, hydrochloric acid, and a gel forming proportion of a mixture of guar gum and glutaraldehyde.

2. The composition of claim 1 having uniformly dis-- persed therein a powdered metal selected from the group consisting of aluminum and magnesium, and mixtures thereof. i t

3. The composition of claim 2 wherein said powdered metal is aluminum. 7 Y

4. The composition of claim 2 wherein said powdered metal is magnesium.

5. An acidic explosive gel composition comprised of a substantially homogeneous mixture containing between about 5 and about 90 percent by weight of ammonium nitrate, between about 3 and about 60 percent by weight of water, between about 0.01 and about 2.0 percent by Weight of hydrochloric acid, between about 0.03 and about 5.0 percent by weight of guar gum, between about 0.03 and about 2.0 percent by weight of glutaraldehyde, and between about 3 and about 5.0 percent by weight of a powdered metal selected from the group consisting of aluminum and magnesium, and mixtures thereof.

6. The composition of claim 5 wherein said powdered metal is aluminum.

7. The composition of claim 5 wherein said powdered metal is magnesium.

8. An acidic explosive gel composition comprised of a substantially homogeneous mixture containing between about 40 and about 70 percent by weight of ammonium v nitrate, between about 20 and about percent by weight of water, between about 0.5 and about 1.0 percent by weight of hydrochloric acid, between about 1.0 and about 3.0 percent by weight of guar gum, between about 0.5

and about 1.0 percent by weight of glutaraldehyde, and between about 10 and about 25 percent, by weight of a powdered metal selected from the. group consisting of aluminum and magnesium, and mixtures thereof.

9. The process for preparing an explosive gel which comprises the steps of admixing an aqueous solution of ammonium nitrate with sufiicie-nt hydrochloric acid to adjust the pH thereof between about 1.5 and about 4.5, adding a gel forming proportion of a mixture of guar gum and glutaraldehyde to said acidic solution, and admixing with said gel a powdered metal selectedfrom the group consisting of aluminum and magnesium, and mixtures thereof.

10. The process of claim 9 wherein the resulting explosive gel contains between about 5 and about 90 percent by weight of ammonium nitrate, between about 3 and about percent by weight of water, between about 0.01 and about 2.0 percent by weight of hydrochloric acid, between about 0.03 and about 5.0 percent by weight of guar gum, between about 0.03 and about 2.0 percent by weight of glutaraldehyde, and between about 3 and about 50 percent by weight of a powdered metal selected from the group consisting of aluminum and magnesium, and mixtures thereof.

11. The process of claim 10 wherein said powdered metal is aluminum.

12. The process or" claim 10 wherein said powdered metal is magnesium.

13. The process of claim 9 wherein the resulting explosive gel contains between about 40 and about percent by weight of ammonium nitrate, between about 20 and about 45 percent by weight of water, between about 0.5 and about 1.0 percent by weight of hydrochloric acid, between about 1.0 and about 3.0 percent by weight of guar gum, between about 0.5 and about 1.0 percent by weight of glutaraldehyde, and between about 10 and about 25 percent by weight of a powdered metal selected from the group consisting of aluminum and magnesium, and mixtures thereof.

14. A stable, non-separating, acidic explosive gel composition comprising a substantially homogeneous mixture containing as its essential ingredients between about 5 and about 90 percent by weight of ammonium nitrate, between about 3 and about 60 percent by weight of water, between about 0.01 and about 2.0 percent by weight of an acid selected from the group consisting of inorganic mineral acids and oxalic acid, between about 0.03 and about 5.0 percent by weight of guar gum, between about 0.03 and about 2.0 percent by weight glutaraldehyde, and between about 3 and about 50 percent by weight of a powdered metal selected from the group consisting of aluminum, magnesium and mixtures thereof. 7

l5. Theprocess of claim 9 wherein said hydrochloric acid is gaseous and is bubbled through said solution of ammonium nitrate to adjust the pH thereof.

16. The process of claim 9 wherein said hydrochloric acid-is added to said solution of ammonium nitrate as an aqueous solution.

17. The process for preparing a stable, non-separating, acidic explosive gel composition comprising a substantially homogeneous mixture containing as its essential ingredients between about 5 and about 90 percent by weight of ammonium nitrate, between about 3 and about 60 percent by weight of water, between about'0.01 and about 2.0

percent by weight of an acid selected from the group consisting of inorganic mineral acids and oxalic acid, between about 0.03 and about 5.0 percent by weight of guar gum, between about 0.03 and about 2.0 percent by weight glutaraldehyde, and between about 3 and about 50 percent by weight of a powdered metal selected from the group consisting of aluminum, magnesium and mixtures thereof, which comprises the steps of admixing an aqueous solution of ammonium nitrate with a suflicient amount of said acid to adjust the pH thereof to between about 1.5 and about 4.5, admixing approximately 70 percent of said guar gum With said ammonium nitrate solution and partially hydrating the same, adding approximately 20 percent of said glutaraldehyde to the resulting mixture, stirring the resulting mixture for several minutes, and thereafter adding the remainder of said glutaraldehyde 5 to the resulting syrupy solution, adding said powdered metal and the remaining of said guar gum to the resulting mixture and stirring the composition for several minutes. 18. The process of claim 17 wherein said mixture of the acidic ammonium nitrate solution and approximately 10 70 percent of said guar gum is hydrated for approximately 2 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN ACIDIC EXPLOSIVE GEL COMPOSITION COMPRISED OF AMMONIUM NITRATE, WATER, HYDROCHLORIC ACID, AND A GEL FORMING PROPORTION OF A MIXTURE OF GUAR GUM AND GLUTARALDEHYDE. 